Find the angles of an isosceles ABC if one of the base angles is A) 25 °, B) 65 °.

To find the angles in an isosceles triangle, we will use one of the properties of such a triangle, namely: an isosceles triangle has equal angles at the base. That is, if, according to the specification, one angle is 25 °, then the second angle at the base is also 25 °. To find the third angle, we use the triangle sum theorem, according to which, the sum of all the angles of a triangle is 180 °. From this theorem it follows that the third angle will be equal to: 180 ° – 25 ° – 25 ° = 130 °.

If one angle at the base is 65 °, then the second angle at the base is also 65 °, and the third is calculated by the formula 180 ° – 2 * 65 ° = 180 ° – 130 ° = 50 °.

Answer: 1) 25 °; 25 °; 130 °; 2) 65 °; 65 °; 50 °.